PURPOSE: To prevent the loosening of a screw produced by the friction of an opening and closing motion, by using a bolt with a spiral screw on the pivot of scissors which rotatively mount a pair of nipping objects around a pivot.

CONSTITUTION: A spiral groove 6 is formed in the pivot hole of a nipping object 3B and a bolt 1 with a spiral screw for a pivot is inserted through the pivot hole of a nipping object 3A. This bolt head part (a) is fixed to the nipping object 3A by a fixing plate 2 and small machine screws. The spiral groove part 6 can thus rotate around the bolt. In this way, by the working of the spiral groove 6, a contact pressure necessary for the cutting element of scissors gradually becomes stronger, as the contact point moves from the root 4 of a cutter to the top 5. On the other hand, by the working of an elastic body 7, the loosening produced by the abrasion of the cutter is absorbed. Furthermore, when the scissors is designed, it is possible to change the magnitude of the contact pressure by changing the pitch of the spiral groove.